Articulated arm transfer device

ABSTRACT

A concentric-shaft rotational drive system for an articulated arm transfer device adaptable for imparting movement to an assembly inside a vacuum chamber wherein rotary movement is imparted to rotors inside the vacuum chamber by means of magnetic fields produced by stators outside the vacuum chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 08/434,012, filed on May 3,1995, now U.S. Pat. No. 5,720,590, which is a continuation ofapplication Ser. No. 08/048,833, filed Apr. 16, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The apparatus of the present invention relates generally to materialtransfer devices. The material transferred might include, but not belimited to, semiconductor wafers, such as Silicon and Gallium Arsenide,semiconductor packaging substrates, such as High density Interconnects,semiconductor manufacturing process imaging plates, such as masks orreticles, and large area display panels, such as Active Matrix LCDsubstrates.

2. Description of the Prior Art

The transfer of delicate silicon wafers or the like between a pluralityof work stations or locations in the manufacture of semiconductordevices presents unique handling problems. The silicon wafers are verydelicate and have highly polished surfaces. When the wafers are abruptlymoved, they tend to slide. This sliding action can cause the siliconwafers to abrade or alternatively can cause damage to their edges ifthey collide.

There are numerous devices described in the prior art for transferringsilicon wafers. For example:

U.S. Pat. No. 3,823,836 discloses an apparatus which includes a supplycarrier with a plurality of ledges to hold the silicon wafers and awithdrawal device having a vacuum chuck. The vacuum chuck is attached toan elevator which raises and lowers the chuck. A horizontal transfer armcoupled to the vacuum chuck is used to transfer the silicon wafer fromthe supply carrier to a desired work station.

U.S. Pat. No. 3,370,595 discloses a wafer transfer handling apparatushaving an indexable carrier for transferring wafers to and from workstations. Wafers enter and leave the wafer carrier on an air slide withthe aid of a wafer ejector acceptor arm having directional air jets. Thewafer ejector acceptor arm controls the driving of the wafers into orout of the carrier from or onto the air slide, which moves the wafers toor from a work station.

U.S. Pat. Nos. 4,062,463, 3,874,525 and 4,208,150 also disclose wafertransfer devices which include either pneumatic components or grippingdevices for handling the wafers.

U.S. Pat. Nos. 4,666,366 and 4,909,701 disclose wafer transfer handlingapparatus having an articulated arm assembly which extends and retractsin a "froglike" motion to transfer an object such as a wafer between aplurality of locations. Two articulated arms are operatively coupledsuch that when one arm is driven by a motor the articulated arms extendand retract in a "froglike" or "frogkick" type of motion. A platform iscoupled to the arms and has the object to be transferred disposedthereon.

U.S. Pat. No. 4,951,601 discloses wafer transfer handling apparatushaving an articulated arm assembly which includes a concentric-shaft,rotational drive system. However, such drive system requires rotaryseals which can contaminate the vacuum chamber. In the drive system ofU.S. Pat. No. 4,951,601 the inner shaft 98 is mounted on a drum 111which is rotated by a cable 113 mounted on a drive 115 which is rotatedby a belt. It appears that the drive 115 rotates in an aperture in thevacuum chamber, thus requiring a rotary seal. The hollow middle shaft 96is mounted on a drum 101 which is rotated by a cable 103 mounted on adrive 100 which is rotated by a belt. It is not clear which componentsare inside the vacuum, but it seems clear that some rotating member mustrotate in an aperture in the vacuum chamber, thus requiring a rotaryseal. The device of the present invention has no such rotary seals. Allbearings of the present invention are entirely within the vacuum, andall rotating parts are entirely within the vacuum.

SUMMARY OF THE INVENTION

The present invention provides a concentric-shaft rotational drivesystem for an articulated arm transfer device adapted to transferobjects, such as silicon wafers, camera lenses, crystal oscillators, orthe like, between a plurality of locations disposed in various axial andradial planes.

The drive system permits the entire articulated arm assembly to berotated in a radial plane. Like the apparatus of the prior art, suchrotation is done when the end effector is not in an extended position.

The drive system also permits the platform assembly to be displaced inan axial direction. The assembly is adaptable for use in a variety ofenvironments, including operation in a vacuum chamber or othercontrolled environment. The assembly may be mounted for movement insidea vacuum chamber with a vacuum seal between the assembly and itssupport.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a central section through a dual-shaft device constructed inaccordance with the invention and connected so as to drive anarticulated arm transfer device of the type disclosed in U.S. Pat. No.5,180,276 to Hendrickson and assigned to the assignee of the instantapplication;

FIG. 2 is a detail of a portion of the central section of FIG. 1;

FIG. 3 is a detail of a portion of the central section of FIG. 2;

FIG. 4 is a plan view of the device of FIG. 1;

FIG. 5 is an isometric sketch of a prior art device;

FIG. 6 is a plan view of the device of FIG. 1 but modified to drive anarticulated arm transfer device of the type disclosed in co-pendingapplication Ser. No. 997,773 filed Dec. 28, 1992 by Eastman and Davisand assigned to the assignee of the present application, now U.S. Pat.No. 5,431,529;

FIG. 7 is a central section along the line 7--7 of FIG. 6; and

FIG. 8 is a central section similar to that of FIG. 1 and showinganother embodiment of the invention in which a single motor and twobrakes are employed.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 through 4, a mounting flange 1 is attached to anapertured region of the bottom wall 2 of a vacuum chamber within whichan articulated arm transfer device 3 is supported. The mounting flangeitself has a central aperture through which two concentric output shaftsextend. The outer shaft is designated 4, and the inner shaft isdesignated 5. At the extremities of the output shafts within the vacuumchamber a pilot bearing 6 separates the shafts and supports them uponeach other. The two shafts are independently rotatable. However, in thepreferred embodiment of the invention the relative motion of the shaftsis limited to one in which they rotate together, and another in whichthey rotate in opposite directions. The former motion serves to rotatethe articulated arm transfer device, and the latter motion serves toextend and retract the articulated arm transfer device.

The inner shaft is longer than the outer shaft, and the extremity of theinner shaft outside the vacuum chamber extends beyond the correspondingextremity of the outer shaft and attains a maximum outer diametercorresponding to that of the outer shaft. A rotor 7 is supported on theouter surface of the outer shaft 4, and a corresponding stator 8 issupported outside the rotor 7. Similarly, a rotor 9 is supported on theouter surface of the inner shaft 5, and a corresponding stator 10 issupported outside the rotor 9. Each stator is part of a drive whichrotates the corresponding shaft. As appears hereinafter, each rotor isinside the vacuum and each stator is outside the vacuum.

Each rotor-stator pair 7,8 and 9,10 may form part of a conventionalbrushless DC motor such as the M & K Series manufactured by MFMTechnology, Inc., 200 Thirteenth Avenue, Ronkonkoma, N.Y. 11779.

Rotary motion is imparted to each shaft by well-known servomechanismtechniques, wherein a suitable signal is applied to the coils of thestators.

The varying position of each shaft as it rotates is detected by asuitable sensing mechanism in combination which a suitable coded disk orthe like. For example, a coded pattern of opaque portions on atransparent disk may be caused to pass between a light source and alight detector. In lieu of such an optical sensing mechanism, a magneticsensing mechanism may be employed wherein a coded pattern of magnetizedportions on a magnetic disk may be magnetically scanned. Alternatively,the sensing mechanism may be mechanical, such as a combination of a gearand a switch, or it may be acoustical, with rotation of each shaftproducing coded clicks of some sort; even electrostatic systems may bedesigned. For purposes of illlustration, and without limiting the scopeof the invention thereto, an optical sensing mechanism will now bedescribed.

A disk 11 is affixed to the outer extremity of the outer shaft 4 by aclamp plate 12. This disk has a coded pattern of opaque portions whichpass between a light-emitting-diode housing 13 and a read head 14, fromwhich a signal is transmitted to the appropriate external circuitthrough a signal feedthrough 15. The light-emitting-diode housing 13,the read head 14, and the signal feedthrough 15 are supported on a drivehousing 16 which is fixed and forms part of a vacuum-tight tubularcasing 17. The rotor 7 is affixed to the outer shaft 4, and the stator 8is affixed to the drive housing 16 by a stator clamp 18, positioned sothat the stator 8 can co-act with the rotor 7; and two bearings 19, 20are provided between the outer shaft 4 and the corresponding drivehousing 16 upon which that drive is mounted. Similarly, a disk 31 isaffixed to the outer extremity of the inner shaft 5 by a clamp plate 32.This disk has a coded pattern of opaque portions which pass between alight-emitting-diode housing 33 and a read head 34, from which a signalis transmitted to the appropriate external circuit through a signalfeedthrough 35. The rotor 9 is affixed to the inner shaft 5, and thestator 10 is affixed to the drive housing 36 by a stator clamp 37,positioned so that the stator 10 can co-act with the rotor 9; and twobearings 38, 39 are provided between the inner shaft 5 and thecorresponding drive housing 36 upon which that drive is mounted.

The drive housings 16, 36 are of special configuration, and provide animportant part of the vacuum-tight casing 17 which separates theevacuated regions of the device from the atmospheric-air regions of thedevice. The two drive housings are similar in shape and are connected toeach other by an adapter 40.

Vertical motion may be imparted to the shafts by vertical movement ofthe drive housings which in turn are supported on two linear slides 41and two lead screws 42. Alternates to the lead screws with rotary motorsmay be linear motors (servo or stepper) or a voice-coil or solenoid. Thevertically movable drive housings are separated from the mounting flangeby suitable bellows 43, and the outer extremity of the outermost drivehousing is closed off by an end cap 44. Thus the entire region withinthe bellows, drive housings and end cap may be evacuated, and frictionalmotion inside this evacuated region is limited to that of the variousbearings.

Each drive housing has a portion which passes between its respectiverotor and stator, and sufficient clearance must be provided between therotor and this part of the drive housing.

A prior art device is shown in FIG. 5. Rotary motion is imparted to thearticulated arm transfer device by rotating the rotate plug. Extensionand retraction of the frog-legs is achieved by counter-rotation of theextend/retract drive shafts. The structure of the present inventionreduces the number and type of seals required by the use of concentricshafts constructed in a particular way. The prior-art device shows thatcontrol may be effected by (1) simple rotation of a shaft and (2)counter-rotation of two shafts. In the device of the invention, (1) isprovided when the concentric shafts rotate together and (2) is providedwhen the concentric shafts counter-rotate. In this device rotary motionis not limited by the basic mechanism, but may continue in eitherdirection for any desired angle.

The three motions (vertical, rotary and extend/retract) may besimultaneously activated to provide any desired trajectory of the endeffector. On the other hand, in some applications all three motions maynot necessarily be activated, and the scope of the invention includesdevices in which only one or two of the aforementioned three motions areactivated.

Referring now to FIG. 4 in conjunction with FIGS. 1-3, the outer shaft 4is connected to one upper arm 51 and the inner shaft 5 is connected tothe other upper arm 52 of an articulated arm transfer device such asthat shown in the aforementioned U.S. Pat. No. 5,180,276. For θ motion(i.e. rotation of the end effectors 53) both rotors 7, 9 turn insynchronism in one direction. For R motion (i.e. extension andretraction of the end effectors 53) each rotor 7, 9 mirrors the otherwith equal but opposite rotation. These motions are computer controlled,using inputs from the two encoders.

When rotors 7, 9 turn in synchronism in one direction, shafts 4, 5 alsoturn in that direction. Referring to FIG. 4, if the shafts 4, 5 turnclockwise, the upper arms 51, 52 also turn clockwise, along with therest of the apparatus shown in FIG. 4. Conversely, if the shafts 4, 5turn counterclockwise, the entire apparatus shown in FIG. 4 turnscounterclockwise. If, on the other hand, the outer shaft 4 turnsclockwise while the inner shaft 5 turns counterclockwise, the upper arm51 will turn clockwise and the upper arm 52 will turn counterclockwise.The resulting movement of both end effectors 53 is downward in FIG. 4.Conversely, if the outer shaft 4 turns counterclockwise while the innershaft 5 turns clockwise, the upper arm 51 will turn counterclockwise andthe upper arm 52 will turn clockwise. The resulting movement of both endeffectors 53 is upward in FIG. 4.

Referring now to FIGS. 6 and 7, the outer shaft 4 has affixed thereto ablock 54 in which the upper slave arm 55 of an articulated arm transferdevice such as that shown in the aforementioned co-pending applicationSer. No. 997,773 is rotatably supported. The upper drive arm 56 of suchan articulated arm transfer device is affixed to the inner shaft 5 so asto rotate therewith. In this case the two shafts rotate in synchronismfor θ motion, but the outer shaft 4 is held fixed and only the innershaft 5 is rotated for radial motion.

If an articulated arm transfer device of the type shown in theaforementioned U.S. Pat. Nos. 4,666,366 and 4,909,701 (such as shown inFIG. 5) is made with two concentric shafts, an outer shaft to rotate thearms in θ motion and an inner shaft to generate extend/retract motion,it is possible to rotate the appropriate shaft combinations with onemotor (and encoder) by using two brakes, one of which will lock theinner shaft to the outer shaft, and the other the outer shaft to thecasing.

If the outer shaft is locked to the casing, and the shoulder assembly ismounted on the outer (rotate) shaft, no rotation of the shoulder will bepossible. Rotation of the inner shaft by a motor attached to it willgenerate extend-retract motion as is now done by the extend/retractmotor of an articulated arm transfer device of the type shown in FIG. 5.

Conversely, if the inner shaft is locked to the outer shaft, noextend/retract motion is possible. If, therefore, the outer shaft/casingbrake is released, rotation of the inner shaft by the motor will resultin simultaneously rotating the outer shaft, and therefore in θ motion.

If both brakes are locked at the end of each motion, and then theappropriate brake is released, one encoder, when its signal is combinedin a computer with the brake command, can indicate the motion of eitherparameter. If greater precision is required, two encoders, as in FIG. 1(11, 31) may be used.

By proper design and use of magnetic and non-magnetic materials, it ispossible to mount all moving parts, including brake shoes and motorrotors, inside of a sealed cylindrical case, while placing the magnetcoils of all components in atmosphere outside the casing. This willeliminate the known outgassing problems and electrical feedthroughswhich degrade performance of systems having active electromagnets invacuum.

While this mechanism will work with any of the extending arm assembliestypical of robots manufactured by the assignee of the instantapplication, a particular advantage is achieved when using theaforementioned arm shown in FIGS. 6 and 7 and used in articulated armtransfer devices of the type disclosed in the aforementioned co-pendingapplication Ser. No. 997,773, in that only one driving shaft is requiredat the shoulder, eliminating the need of gearing on top of the rotatingshafts.

Referring now to FIG. 8, a mounting flange 61 is attached to anapertured region of the bottom wall of a vacuum chamber within which anarticulated arm transfer device 62 is supported. The articulated armtransfer device 62 is shown as being of the type shown in FIGS. 4 and 5.The mounting flange itself has a central aperture through which twoconcentric output shafts extend. The outer shaft is designated 63, andthe inner shaft is designated 64. At the extremities of the outputshafts within the vacuum chamber a pilot bearing 65 separates the shaftsand supports them upon each other. The two shafts are independentlyrotatable. However, in the device of FIG. 8 only one shaft is rotatablydriven by a motor, and rotation of the other shaft is determined by twobrakes, one of which causes the shafts to rotate together, and anotherof which causes the other shaft to remain fixed. The former motionserves to rotate the articulated arm transfer device, and the lattermotion serves to extend and retract the articulated arm transfer device.

The inner shaft is longer than the outer shaft, and the extremity of theinner shaft outside the vacuum chamber extends beyond the correspondingextremity of the outer shaft. A brake 66 comprising a disk 67 ofmagnetic material is supported on the outer surface of the outer shaft63, and cooperates with a disk 68 of magnetic material which is slidablysupported inside a casing 69 of non-magnetic, vacuum-tight material. Amagnetic coil 70, when energized, magnetizes the disks 67, 68 so thatthey press against each other and act as a brake, preventing rotation ofthe outer shaft 63. Similarly, a brake 71 comprising a disk 72 ofmagnetic material is supported on the outer surface of the outer shaft63, and cooperates with a disk 73 of magnetic material which is slidablysupported on the inner shaft 64. A magnetic coil 74, when energized,magnetizes the disks 72, 73 so that they press against each other andact as a brake or coupling locking the shafts to each other. A motor 75,constructed similarly to the construction of rotor 9 and stator 10 ofFIG. 1, serves to rotate the inner shaft 64. More specifically, a rotor76 is supported on the outer surface of the inner shaft 64, and acorresponding stator 77 is supported outside the rotor 76. The stator 77is part of a drive which rotates the inner shaft 64. The rotor 76 isinside the vacuum and the stator 77 is outside the vacuum.

The rotor-stator pair 76, 77 may form part of a conventional brushlessDC motor such as the M & K Series manufactured by MFM Technology, Inc.,200 Thirteenth Avenue, Ronkonkoma, N.Y. 11779.

Rotary motion is imparted to the inner shaft 64 by well-knownservomechanism techniques, wherein a suitable signal is applied to thecoils of the stator 77.

A disk 78 is affixed to the outer extremity of the inner shaft 64. Thisdisk has a coded pattern of opaque portions which pass through asuitable encoder 79 (which may comprise, for example, alight-emitting-diode housing and a read head, from which a signal istransmitted to the appropriate external circuit through a signalfeedthrough). The shafts 63, 64 are supported upon suitable bearings 65,80 between the shafts 63, 64 and suitable bearings 81, 82 between theouter shaft 63 and the casing 69.

The casing 69 is of special configuration, and provides an importantpart of the wall which separates the evacuated regions of the devicefrom the atmospheric-air regions of the device.

Vertical motion may be imparted to the shafts by vertical movement ofthe casing 69 in a manner hereinbefore described in connection with FIG.1.

The casing 69 has a portion which passes between the rotor 76 and stator77, and sufficient clearance must be provided between the rotor 76 andthe casing 69.

Having thus described the principles of the invention, together withillustrative embodiments thereof, it is to be understood that althoughspecific terms are employed, they are used in a generic and descriptivesense and not for purposes of limitation, the scope of the inventionbeing set forth in the following claims.

I claim:
 1. A transport apparatus having a movable arm assembly operablyconnected to a drive mechanism, the drive mechanism comprising:a housinghaving a chamber; electromagnetic stators stationarily connected to thehousing at different heights relative to the chamber, the stators beinglocated outside of the chamber; a drive shaft assembly located, at leastpartially, in the chamber, the assembly including two independentlyrotatable coaxial shafts, a first one of the shafts extending coaxiallythrough a second one of the shafts, one of the shafts having a set ofpermanent magnets that are aligned with a first one of theelectromagnetic stators; and a first brake system having two disksseparately connected respectively to the two coaxial shafts, wherein afirst one of the disks is located at a second one of the electromagneticstators and, when the second electromagnetic stator is energized, thefirst disk is magnetically moved into contact with a second one of thedisks to lock the two coaxial shafts to each other.
 2. An apparatus asin claim 1 wherein the first disk is slidably supported on the firstshaft.
 3. An apparatus as in claim 1 wherein the first disk is comprisedof magnetic material.
 4. An apparatus as in claim 1 further comprisingmeans for independently sensing angular position of the first shaftrelative to the housing.
 5. An apparatus as in claim 4 wherein the meansfor sensing includes an optical disk connected to the first shaft and adisk reader stationarily connected to the housing.
 6. An apparatus as inclaim 1 further comprising a second brake system having two disksseparately connected to the second shaft and the housing, respectively.7. An apparatus as in claim 6 wherein the second brake system has athird electromagnetic stator which, when energized, moves the disks ofthe second brake system into contact with each other.
 8. An apparatus asin claim 6 wherein the two disks of the second brake system arecomprised of magnetic material.
 9. An apparatus as in claim 6 whereinone of the two disks of the second brake system is slidably supported onthe housing.
 10. A transport apparatus having a movable arm assemblyoperably connected to a drive mechanism, the drive mechanismcomprising:a housing having a chamber; a drive shaft assembly located,at least partially, in the chamber, the assembly including twoindependently rotatable coaxial shafts, a first one of the shaftsextending coaxially through a second one of the shafts; a drive systemfor moving at least one of the shafts relative to the housing, the drivesystem including a first electromagnetic coil stationarily connected tothe housing; a brake system having two disks, a first one of the disksbeing connected to the housing and a second one of the disks beingconnected to one of the coaxial shafts; and a second electromagneticcoil connected to the housing spaced from the first electromagneticcoil; wherein the two disks are located at the second electromagneticcoil and, when the second electromagnetic coil is energized, the twodisks are moved into contact with each other to thereby prevent rotationof the second shaft relative to the housing.
 11. An apparatus as inclaim 10 wherein the first disk is slidably supported on the housing.12. An apparatus as in claim 10 wherein the first disk is comprised ofmagnetic material.
 13. An apparatus as in claim 10 further comprisingmeans for sensing angular position of the first shaft relative to thehousing.
 14. An apparatus as in claim 13 wherein the means for sensingincludes an optical disk connected to the first shaft and a disk readerstationarily connected to the housing.
 15. An apparatus as in claim 13wherein the means for sensing angular position comprises an optical diskconnected to the first coaxial shafts, a light emitter connected to thehousing, and a light read head connected to the housing, the opticaldisk being located between the light emitter and the light read head andhaving a coded pattern of opaque portions, wherein the light read headis adapted to output a signal indicative of angular position of thefirst coaxial shaft relative to the housing based upon light passingthrough a portion of the coded pattern in front of the light read head.16. An apparatus as in claim 10 further comprising another brake systemhaving two additional disks connected to the two coaxial shafts,respectively, and a third electromagnetic coil connected to the housingwhich, when energized, moves the two additional disks of the anotherbrake system into contact with each other.